JP2977196B2 - Mining method of methane hydrate existing in the seabed formation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mining methane hydrate existing in a submarine stratum.

[0002]

Methane hydrate is a substance in which natural gas mainly composed of methane gas is solidified in a sherbet shape together with water under low-temperature and high-pressure conditions. Under the frozen ground, in the sea area, it exists in the seafloor depth of several hundred meters below the seafloor around the continental shelf. The estimated reserves of methane hydrate, especially methane hydrate existing in the sea, are enormous and are expected as next-generation energy resources.

[0003] Conventionally, oil and natural gas resources are mined in the sea area using marine production facilities represented by fixed or floating platforms on the sea floor. When mining oil or natural gas, there is little possibility that large stress fluctuations will be applied to the ground in the submarine stratum. This is because the petroleum or natural gas layers do not form part of the structural support in the seafloor formation, because the oil or natural gas is not a solid but a liquid or gas. On the other hand, since methane hydrate is a solid as described above, it often forms a part of the structural support in the undersea stratum. Therefore, when mining the methane hydrate layer,
It may cause large stress fluctuations in the ground of the seafloor stratum, causing large-scale collapse of the ground. For this reason, mining methods using marine production facilities have many problems from the viewpoint of safety in the case of methane hydrate. In addition, when mining methane hydrate, methane hydrate may be gasified and explode. Therefore, there is a problem that mining must be performed while paying sufficient attention to safety.

[0004] Accordingly, an object of the present invention is to provide a method for safely mining methane hydrate existing in a submarine stratum.

[0005]

According to a first aspect of the present invention, there is provided a method for mining methane hydrate existing on a seabed, wherein the method comprises the steps of: exposing a methane hydrate layer from land adjacent to the seabed having a methane hydrate layer; Drilling a tunnel tunnel to a depth to make it, drilling a horizontal tunnel 70m to 100m in front of the methane hydrate layer toward the methane hydrate layer, and injecting cement into the ground around the tip of the horizontal tunnel to cover lock. Forming, drilling from the tip of the horizontal tunnel towards the methane hydrate layer, passing a first pipe through the methane hydrate layer, and injecting hot steam from the first pipe into the methane hydrate layer, Separate methane hydrate into gas and water and aspirate through second and third pipes Thereby extracting gas and water from the methane hydrate layer, respectively, and transferring the extracted gas by a fourth pipe laid to the land through a horizontal tunnel and a shaft tunnel. Is what you do.

[0006]

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. First, as shown in FIG. 1, a shaft tunnel 12 is excavated from a land 10 adjacent to a submarine stratum where a methane hydrate layer exists.
After excavating the shaft tunnel 12 to the depth where the methane hydrate layer exists, the horizontal tunnel 14 is excavated toward the methane hydrate layer.

[0008] 70m-10 before the methane hydrate layer
At 0 m, a cover lock 16 is formed at the tip of the horizontal tunnel 14. The cover lock 16 is formed by performing a plurality of borings 18 and injecting cement into the ground in front of the tip of the horizontal tunnel 14, as shown in FIG. The cover lock 16 structurally strengthens the ground in front of the tip of the horizontal tunnel 14 and also serves to stop water.

The length of the cover lock 16 is preferably
It is 50 m to 70 m.

Next, drilling is performed from the tip of the horizontal tunnel 14 toward the methane hydrate layer, and a pipe 20 is passed through the methane hydrate layer as shown in FIG. When high-temperature steam is injected from the pipe 20 into the methane hydrate layer, the temperature of the methane hydrate rises and is separated into gas and water. Gas and water are extracted from the methane hydrate layer by suction through pipes 22,24. The gas thus extracted is transferred by a pipe (not shown) laid to the land 10 through the horizontal tunnel 14 and the shaft tunnel 12.

[0011]

According to the present invention, methane hydrate can be safely mined without using a marine production facility.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an outline of a method of the present invention.

FIG. 2 is a schematic view showing formation of a cover lock.

FIG. 3 is a conceptual diagram schematically showing separation of methane hydrate by injection of high-temperature steam.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Land 12 Shaft tunnel 14 Horizontal tunnel 16 Cover lock 18 Boring 20, 22, 24 Pipe

Claims (1)

(57) [Claims] Claims: 1. A method for mining methane hydrate existing in a seabed, comprising: excavating an inclined shaft tunnel from a land adjacent to a seabed where a methane hydrate layer exists to a depth where a methane hydrate layer exists; 70 before the methane hydrate layer toward the methane hydrate layer
excavating a horizontal tunnel to a point of m to 100 m, forming a cover lock by injecting cement into the ground around the tip of the horizontal tunnel, boring from the tip of the horizontal tunnel toward the methane hydrate layer, and forming a first pipe Into the methane hydrate layer and inject hot steam into the methane hydrate layer from the first pipe to separate the methane hydrate into gas and water and aspirate through the second and third pipes Gas and water are respectively extracted from the methane hydrate layer, and the gas thus extracted is transferred by a fourth pipe laid to the land through a horizontal tunnel and a shaft tunnel. And how.